In a case that pits the constitutional rights of students against the job protections of teachers, a Los Angeles County Superior Court judge approved a groundbreaking settlement Friday that limits the effect of layoffs on the district's most vulnerable students.

Up to 45 Los Angeles Unified School District campuses will be shielded from teacher layoffs altogether, Judge William F. Highberger ordered Friday, and layoffs in the district's other 750 schools must be spread more equitably. That could lead some experienced teachers to lose their jobs.

The decision comes amid deep education cuts and a debate over teacher tenure rules, which are being challenged across the country. New Jersey Gov. Chris Christie recently called for the end of tenure, as have leaders in Florida, Idaho, Wyoming and elsewhere.

"This year, if we are forced to lay off teachers, we will be forced to lay off some of the most effective, and keep some of the least effective," New York City Mayor Michael Bloomberg said in a speech this week. "It's not right. It's not fair. And it's not something we can allow to happen."

Locally, L.A. Unified faces a nearly $400-million shortfall that could force thousands more teachers out of the classroom this year.

Lawyers representing district students hailed the judge's ruling as a "landmark victory" that put the interests of children ahead of their instructors.

"The court today handed these children an umbrella in a hurricane," said Mark Rosenbaum, legal director for the Los Angeles office of the American Civil Liberties Union which, along with Public Counsel and several other public interest law firms, brought the suit on behalf of students.

Representatives of United Teachers Los Angeles, which vigorously opposed the settlement in court, said the teachers union will probably appeal the order, which "eviscerates seniority" and will damage the morale of district teachers.

"We do not agree with the remedy that the court is mandating," said Julie Washington, a union vice president.

Washington and other union leaders have said the district needs to find a way to better train instructors and administrators and help students from impoverished backgrounds.

The settlement is an attempt to address a problem all parties recognize: the devastating effect that layoffs have had on district campuses in recent years. Some schools have lost as much as 50% of their teaching staffs to cutbacks, unraveling some reform efforts and causing turmoil at already struggling campuses.

A Times investigation last year found that seniority-based layoffs in the district had led to the dismissal of hundreds of highly effective teachers and fell hardest on schools in the city's poorest neighborhoods. Far fewer layoffs would be necessary if the decisions were based on performance rather than seniority, a Times analysis found.

In February 2010, civil rights attorneys representing students at three district middle schools filed a class-action lawsuit arguing that that the layoffs, which under state law are based exclusively on seniority, had a disproportionate effect on poor and minority students.

Highberger granted an injunction last March that blocked further layoffs at those schools and in December tentatively approved a settlement between the school district and the students' attorneys that allowed some schools to be exempted from future layoffs.

During a three-day hearing, the teachers union urged the court to reverse its decision and order a deeper examination of the causes of high turnover at troubled schools.

Richard Ingersoll, an education expert for the union, argued that the settlement would "divert attention from the real problem, which is that these schools are a leaky bucket."

Tom Torlakson, the state's newly elected superintendent of public instruction, submitted a brief echoing the teachers' union position on Friday, saying that districts already have the ability to dismiss instructors based on factors other than seniority. State law allows for some exceptions for teachers with special skills or credentials.

Torlakson asserted that teachers union officials were not part of settlement negotiations, a statement that district officials and other attorneys dispute.

A spokeswoman for Torlakson, who was heavily supported by teachers unions during his campaign, said he was unavailable for comment but that the brief was based on the "merits of the case."

The 45 protected schools have not yet been identified, and union lawyers objected to the discretion given to the district to name 20 of them.

John Deasy, incoming Los Angeles schools superintendent, said district officials would begin determining this weekend which schools would be exempted and how that would affect expected layoffs. The district must send preliminary layoff notices by March 15 and the board must approve them before then.